Syracuse, N.Y. -- Air quality is improving in Central New York where Onondaga County is ranked one of the cleanest counties in the nation for short-term particle pollution, according to a report released today.

The annual report by the American Lung Association grades counties with air quality monitors for ozone and particle pollution based on data collected from the U.S. Environmental Protection Agency from 2008 through 2010.

Ozone, or smog, is the most widespread air pollutant. It is a gas formed when sunlight reacts with vapors emitted from motor vehicles, factories and power plants. Breathing in ozone irritates the lungs and can cause asthma attacks, coughing, wheezing, chest pain and premature death.

Particle pollution is a mixture of ash, soot, diesel exhaust, chemicals, metals and aerosols. It can cause asthma, heart attacks, strokes, lung cancer and early death.

Oswego County improved from a D to a B for ozone pollution, according to the report. Madison and Onondaga counties improved their ozone grades from D to C, while Herkimer and Oneida improve from C to B.

The report said that while significant progress is being made to clean up air pollution across the state, far too many New Yorkers still breathe unhealthy air.

Six of the 34 counties in New York with air quality monitors received failing grades in the report.

Onondaga County received a grade of A for short-term particle pollution. It was the only county in Central New York monitored for this type of air pollution.